Process and composition for improving the properties of fibrous cellulosic material



United States Patent PROCESS AND COMPOSITION FOR MPROVING THE PROPERTIES OF FIBROUS CELLULOSIC MATERIAL Charles B. Ratclilfe, Chickasaw, and Harold F. Wise, Spring Hill, Ala., assignors to Courtaulds, Inc., New York, N.Y., a corporation ofDelaware No Drawing. Application September 6, 1956 Serial No. 608,218

"' 16 Claims. (Cl. 117-145) This invention relates to a process and composition for improving the properties of fibrous cellulosic material and in particular to a process and composition whereby the water imbibition of regenerated cellulose fibers may be decreased without rendering them unduly brittle.

Regenerated cellulose fibers are widely used in a variety of different textile applications. One factor which has somewhat limited their utility, however, is that they absorb moisture readily and in so doing become weak. The extent to which water is absorbed by a given fiber is measured by its water imbibition. This is defined as the percent by weight of waterretained in saturated material after centrifuging a 0.5 gram sample for 5 minutes at a centripetal acceleration of 1000 g. or one thousand times the acceleration due to gravity and is expressed as percent of the oven dry weight of the fiber. See Journal of the Society of Dyers and Colourists, October 1948, page 331, and Proceedings, Journal of the Textile Institute 40, page P678 (1949).

To decrease the water imbibition of cellulose fibers it has been proposed to treat the fibers with heat-hardenable synthetic resins. Among the resins used for this purpose are those having as the principal ingredient, heat-hardenable resinous materials of the general type known as aminoplasts. This term has come into general use in the art and is used herein to mean heat-hardenable resinous compositions which are the condensation products of compounds having at least two amino hydrogens, with methylol-forming compounds. Among the more common aminoplasts are urea-formaldehyde, melamine-formaldehyde, dicyandiamide-formaldehyde, and guanidine-formaldehyde resins. Other classes of resins which have been proposed for the treatment of regenerated cellulose fibers are the acrolein-formaldehyde resins, formed by the condensation of acrolein with formaldehyde as described, for example, in US. Patent 2,696,477, and resins containing acrolein and urea together with formaldehyde.

In applying these resinous finishes, an aqueous solution or dispersion of a resinous precondensate is generally first made up. In the precondensate, the principal ingredients, eg. urea and formaldehyde, are reacted but not to the extent that they become insoluble in water, or infusible. The aqueous solution or dispersion is then applied to the fibrous material and the material is dried and then heated to cure the resin with which it has been impregnated.

One difiiculty which has been experienced with resinous finishes of the type described has been that they embrittle the fibers to the extent that the fibers become diflicult to handle in textile processing machinery. This is especially true of staple fiber which must undergo a number of different steps such as carding, spinning, and the like, before it is finally put into fabric form.

The present invention is based on the discovery that if the fiber is impregnated with a water-soluble ketone in addition to the resin, prior to curing, a fibrous product is obtained which is far less brittle, has a better hand, and is more easily processed than would be the case "ice were only the resin used. At the same time, the decrease in water imbibition obtained by use of the resin material is in no way diminished.

The present invention, therefore, provides a process for improving the properties of fibrous cellulosic materials which comprises impregnating regenerated cellulose fiber with a heat-hardenable resinous material and with a water-soluble ketone and then curing the resin.

impregnation of the fiber by the ketonemay be accomplished either before, simultaneously with, or after impregnation by the resinous material. Preferably, however, the ketone is put into an aqueous solution or dispersion of resinous precondensate and both are applied at the same time.

The invention therefore further provides a composition for improving the properties of textile materials comprising an aqueous liquid containing between about 5 and about 15% by weight of a resinous precondensate selected from the group consisting of aminoplasts, acrolein-formaldehyde and acrolein-urea-formaldehyde precondensates and between about 1 and about 10% by weight of a water-soluble ketone.

Among the ketones which can be used are those which have a solubility in water of at least 4 parts by weight per 100 parts per water. .In this group are included acetone, butanone, diethylketone, sorbose, and mesityl oxide. Of these, acetone is preferred as being most readily available and least expensive. The amount of ketone used is preferably between 1 and about 10% on the weight of the total impregnating solution. Since the fiber will normally take up about -100% based on its own dry weight of an impregnating liquid, the amount of ketone retained on the fiber, based on the weight of the fiber, will be between about 0.8% and about 10% by weight. g

The amount of resin applied to the fiber will vary depending on the particular resin being used and the properties desired in the finished product. In general, it will be between about 4 and about. 15% by weight based on the weight of the dry fiber.

Regenerated cellulose fibers may be treated in accordance with the present invention at any time subsequent to their regeneration. Preferably, however, they are treated while still wet from the initial processing baths. Thus, it is well known in the viscose art to extrude cellulose xanthate into an acid bath to coagulate the fibers, then treat the fibers further with acid to regenerate them, wash the fibers to remove the acid, wash again with a dilute alkali to remove sulphur, and wash again to remove the alkali. Often, other treatments involving washing of the fiber are also given to the newly spun material.

In accordance with a preferred embodiment of the invention, the resin and ketone impregnation step or steps is given to the newly spun fibers at the end of this series of conventional baths, and before the fibers are dried. After the resin-ketone impregnation, the fibers may be dried at a temperature of say 80 to C., but in any case not substantially above the boiling point of water, and after being dried may be subjected to a higher temperature to cure the resin. This higher temperature will of course depend upon the particular type of resin being used, but is generally on the order of above C., say 130 to C.

Although the procedure outlined is preferred, it should be understood that the mixture of resin and acetone, or the acetone separately, can be applied at any point in the processing cycle after regeneration of the cellulose fiber, and may be applied even after the fiber has been dried.

The temperature at which the ketone or ketone-resin dispersion is applied to the fibers is not critical. Usually 3 it is between about 20 C. and about 35 C. The ketone or ketone-resin dispersion may be applied in any convenient way as, for example, by passing the fibers through a bath of the ketone or dispersion or by spraying the ketone or dispersion onto the fibers.

The exact function of the ketone in reducing brittleness of the fiber is not well understood. However, it is believed to aid in the penetration of the resin to the interior of the individual cellulose fibers. It is thought that by aiding the resinous material to penetrate the fibers, the presence of a stiff brittle sheath or outer coating on the fibers is avoided.

The invention will be further described with reference to the following specific examples, it being understood that these examples are given for the purpose of illustration only and are not to be taken as in any way restricting the invention beyond the scope of the appended claims.

In carrying out the specific examples, newly made viscose fiber of 1 /2 denier, 1%," long, which had never been dried, was dipped into a solution, prepared as indicated in the particular examples and at a temperature of about 25 C. allowed to soak for two minutes, and then centrifuged for three minutes to remove excess solution. The fiber was then opened by hand and drying was performed in an oven at 100 C. for one hour. Curing was then accomplished by heating in the same oven for seven minutes at 166 C. The finished samples were then tested for water imbibition and fiber brittleness. In the examples, the percentages are by weight unless otherwise specified.

Example I Newly spun never-dried viscose rayon fiber was soaked for two minutes in an aqueous solution consisting essentially of urea formaldehyde precondensate (mole ratio urea: formaldehyde of 1.6:1) 17%; catalyst (MgCl .6H O) 0.75%, and acetone, 5%. After centrifuging, drying and curing, as indicated above, it was found that fiber softness and color were normal and water imbibition was 36%. There was a general lack of loose broken fragments, in sharp contrast to a control sample which was treated as indicated with a solution containing the same resin, and catalyst, but no acetone. In this case, water imbibition was 42.9% and brittle fibers were well in evidence when the sample was crumbled by hand.

Example II The procedure indicated in Example I was followed except that the acetone was applied separately rather than in the resin solution. Specifically, the newly spun undried fiber was soaked in acetone for five minutes. Excess acetone was squeezed out by hand and the fiber was then treated with an aqueous solution consisting essentially of urea formaldehyde precondensate (mole ratio urea: formaldehyde of 1.6:1) 17% and catalyst (MgCl .6H O) .75%. Water imbibition was 43.4% and there was no discoloration. No loose broken fragments were noticeable.

Example 111 Fiber was treated as in Example I but with an aqueous solution consisting essentially of urea formaldehyde precondensate (mole ratio urea: formaldehyde of 1.6:1) 17% catalyst (MgCl .6I-I O) .75%; butanone 5%. The resulting fibers were normal in color and handle. A water imbibition of 46.6% was obtained. The fiber had a satisfactory hand and much reduced brittleness, compared with a similar sample treated with resin but without ketone.

Example 1V Fiber was treated as in Example I with an aqueous solution consisting essentially of urea-formaldehyde precondensate (mole ratio urea: formaldehyde of 1.61:1) 17% catalyst (MgCl .6H O) .75%; diethylketone, 5%. Water imbibition of this sample was 51.7%. No change was noted in fiber color. Brittleness was reduced compared with a similar treatment omitting the ketone.

Example V The procedure of Example I was carried out using the following aqueous solution: urea formaldehyde precondensate (mole ratio urea: formaldehyde of 1.6:1) 17%, catalyst (MgCl .6H 0) .75%; diacetone alcohol, 5%. A water imbibition of 48.3% was obtained from this run with fiber color and handle remaining normal. The degree of fiber brittleness was comparable to that of fiber treated with acetone.

Example VII The procedure of Example I was carried out using an aqueous solution consisting essentially of urea formaldehyde precondensate (mole ratio urea: formaldehyde of 1.6:1) 17%, catalyst (MgCl .6H O) .75%; sorbose, 5% Fibers resulting from this treatment had normal color and hand, and a water imbibition of 49.9%. A good reduction in fiber brittleness was obtained.

Example VIII The procedure of Example I was carried out using the following composition: melamine-formaldehyde precondensate (mole ratio, melamine: formaldehyde of 23:1), 4%; catalyst (MgCl 0.75%; acetone 5%. A water imbibition of 41% was obtained and yarn color was normal. Indications of fiber brittleness were almost completely absent.

Example IX The procedure of Example I was carried out using the following aqueous solution: urea-formaldehyde (mole ratio, urea: formaldehyde of 1.6:1) 17%; catalyst (Mgcl 0.75%; acetone 1%.

In this example, water imbibitions of 42.9% were obtained and yarn color and handle were normal. Indications of fiber brittleness were scarcely detectable.

Example X The procedureof Example I was followed using the following aqueous solution: acrolein-urea-formaldehyde (mole ratio, 1:2:7.5) 20%; catalyst (Mgcl 0.75%, acetone 5%. A water imbibition of 49% was obtained in this case, the fibers being normal in color and hand. Indications of fiber brittleness were almost completely absent.

Example XI The procedure of Example I was followed using the following aqueous solution: urea-formaldehyde (mole ratio, urea: formaldehyde, 1.6:1) 17%; catalyst 0.75% acetone 10%.

In this example, water imbibitions of 48.8% were obtained and yarn color and handle were normal. No brittleness was observed. No change was evident to yarn color in handle.

It will be obvious that many variations of the invention are possible and will occur to those skilled in the art. For example the process and compositions disclosed may be applied to yarn or to woven or knitted fabrics as well as to staple fiber, with beneficial results.

What is claimed is:

1. A process for improving the properties of regenerated cellulosic fibrous materials which comprises impregnating regenerated cellulose fiber with a heat-hardenable resinous material and with a water-soluble ketone having a water solubility of not less than about 4 parts by weight in 100 parts of water; and subsequently curing said resinous material.

2. The process claimed in claim 1 wherein impregnation with the water-soluble ketone is carried out prior to impregnation with the resinous material.

3. The process claimed in claim 1 wherein impregnation with the water-soluble ketone and impregnation with the resinous material are carried out simultaneously.

4. The process claimed in claim 1 wherein the heathardenable resinous material is selected from the group consisting of aminoplast and acrolein-formaldehyde precondensates.

5. The process claimed in claim 1 wherein the amount of water-soluble ketone applied to the fiber is between about 0.5 and about 10% on the weight of the dry fiber.

6. The process claimed in claim 1 wherein the watersoluble ketone is selected from the group consisting of acetone, butanone, diethylketone, diacetone alcohol, and sorbose.

7. The process claimed in claim 6 wherein the watersoluble ketone is acetone.

8. A process for improving the properties of regenerated cellulosic fibrous material which comprises impregnating said material with between about 80 and about 100% by weight of an aqueous liquid containing between about and about 15% by weight of a heat-hardenable resinous precondensate selected from the group consisting of aminoplast and acrolein-formaldehyde precondensates, and between about 1 and about of a ketone having a water solubility of not less than about 4 parts by weight in 100 parts of water; then drying the impregnated fiber, and heating the fiber to cure the resin.

9. The process claimed in claim 8 wherein the watersoluble ketone is acetone.

10. A treating composition for improving the properties of textile materials comprising an aqueous liquid containing between about 5 and about 15% by weight of a resinous precondensate selected from the group consisting of aminoplast and acrolein-formaldehyde precondensates and between about 1 and about 10% by weight of a water-soluble ketone having a water solubility of not less than about 4 parts by weight in 100 parts of water.

11. The composition claimed in claim 10 wherein the ketone is acetone.

12. The process claimed in claim 1 wherein the heathardenable resinous material is an acrolein-urea-formaldehyde precondensate.

13. A process for improving the properties of regenerated cellulosic fibrous material which comprises impregnating said material with between about and about by weight of an aqueous liquid containing between about 5 and about 15% by weight of an acrolein-ureaformaldehyde precondensate, and between about 1 and about 10% of a ketone having a water solubility of not less than about 4 parts by weight in 100 parts of water; then drying the impregnated fiber, and heating the fiber to cure the resin.

14. The process claimed in claim 13 wherein the watersoluble ketone is acetone.

15. A treating composition for improving the properties of textile materials comprising an aqueous liquid containing between about 5 and about 15 by weight of an References Cited in the file of this patent UNITED STATES PATENTS Hessel et a1. Apr. 9, 1946 Wright et al Mar. 13, 1956 

1. A PROCESS FOR IMPROVING THE PROPERTIES OF REGENERATED CELLULOSIC FIBROUS MATERIALS WHICH COMPRISES IMPREGNATING REGENERATED CELLULOSE FIBER WITH A HEAT-HARDENABLE RESINOUS MATERIAL AND WITH A WATER-SOLUBLE KETONE HAVING A WATER SOLUBILITY OF NOT LESS THAN ABOUT 4 PARTS BY WEIGHT IN 100 PARTS OF WATER, AND SUBSEQUENTLY CURING SAID RESINOUS MATERIAL. 